The gas bearing has the advantages of being high in speed, high in precision, resistant to high temperature and small in friction loss, long in service life and the like. After the rapid development of recent decades, the gas bearing has been widely applied to the fields of high-speed supporting, high-precision supporting and the like. At present, various types of gas bearings have been developed, and the gas bearings are mainly divided into a dynamic pressure type and a static pressure type.
The dynamic pressure gas bearing takes gas as a lubricant, and a gas film is formed between the shaft and the bearing. It is a bearing form that the moving face is not in direct contact with the static face, and it has many advantages such as no pollution, low friction loss, wide temperature range, smooth operation, long use time and high working speed. Due to the small friction loss, and not necessary to use liquid lubricating oil, it is widely used in the field of high-speed rotary applications. In particular, it is often used in ultra-high-speed application field which is usually supported by a rolling bearing and where liquid lubricants are not suitable.
The dynamic pressure gas bearing in accordance with the direction of bearing load is divided into a dynamic pressure gas radial bearing, a dynamic pressure gas thrust bearing and a dynamic pressure radial thrust combined bearing. The dynamic pressure gas radial bearing is formed by the relatively moving two working faces forming a wedge-shaped space. When they are relatively moved, the gas is driven by its own viscous action and compressed into the wedge-shaped gap, thereby generating dynamic pressure to support the load. Different structural forms of gas dynamic pressure radial bearings due to structural differences, the work process is slightly different. At present, the more common types of dynamic pressure radial bearing structure are a tilting pad type, a groove type and a foil type.
The tilting pad type dynamic pressure gas radial bearing is a kind of excellent dynamic pressure gas bearing with self-adjusting performance, which can work safely in the space of smaller air gap, and is not sensitive to thermal deformation, elastic deformation and so on, and the machining precision is easy to be guaranteed, and it has the outstanding advantages of being capable of automatically tracking the change of the load. At present, it is mainly used in large-scale high-speed rotating machinery and turbine machinery at home and abroad. But its bearing structure is more complex, the installation process is complex, is higher than the general radial bearing requirements, thus its application is limited.
Although the foil type dynamic pressure radial bearing with elastic support, can make the bearing to obtain a certain bearing capacity and alleviate the impact vibration capacity, but the foil bearing is usually made of metal foil sheets, there are still some problems in the material manufacturing technology and processing technology, the damping value of the bearing can not be greatly improved, so that the rigidity of the bearing is not enough, the critical rotating speed of the bearing is low, and the bearing is easy to instability and even stuck during high-speed operation.
The groove type dynamic pressure gas radial bearing has good stability, and the certain stability is achieved even under no load; moreover, at a high speed, the static bearing capacity is larger than that of other forms of bearings. But the existing groove-type dynamic pressure gas radial bearing can only achieve the load capacity of 0.5-1.5 kg and can only reach the maximum limit rotating speed of 100,000 rpm-200,000 rpm, it can not meet the application of the ultra-high speed field under a large load.